Networks enable computers and other devices to communicate. For example, networks can carry data representing video, audio, e-mail, and so forth. Typically, data sent across a network is divided into smaller messages known as packets. By analogy, a packet is much like an envelope you drop in a mailbox. A packet typically includes “payload” and a “header”. The packet's “payload” is analogous to the letter inside the envelope. The packet's “header” is much like the information written on the envelope itself. The header can include information to help network devices handle the packet appropriately. For example, the header can include an address that identifies the packet's destination.
A given packet may “hop” across many different intermediate network forwarding devices (e.g., “routers”, “bridges” and/or “switches”) before reaching its destination. These intermediate devices often perform a variety of packet processing operations. For example, intermediate devices often perform packet classification to determine how to forward a packet further toward its destination or to determine the quality of service to provide.
Processing packets creates a variety of computational burdens. For example, on intermediate nodes, forwarding or filtering decisions need to be made for each packet. The heavy volume of network traffic makes fast processing of packets of vital importance. Likewise, packet processing consumes processing resources at the packet's destination where the payloads of packets are “unloaded” and reassembled into a stream of data for an application. As speeds increase, the burden of processing network traffic can rob applications of processor resources.